The adhesive extracellular matrix (ECM) glycoprotein fibronectin is ubiquitously distributed along NC migration pathways in the Xenopus embryo (Davidson et al., 2004). CNC undergoes cell migration on immobilized fibronectin substrates in vitro and exhibits a similar stream formation as demonstrated in vivo (Sadaghiani and Thiébaud, 1987; Alfandari et al., 2003). To further analyze the role of DS-epi1 in cell migratory behavior, we cultured CNC explants on fibronectin-coated plates (Fig. 6F). At 2 h after plating, one side of the uninjected CNC explants had expanded, and cells had spread on the substrate and migrated as a cohesive sheet (Fig. 6G). After 4 h, distinct segments started to form that were reminiscent of the mandibular, hyoid and branchial streams (Fig. 6G′). In contrast, the Dse-MO-injected CNC cells acquired a round morphology after 30 min, and did not subsequently spread or migrate (Fig. 6H,H′ and data not shown). To visualize the cytoskeleton, we performed phalloidin staining ∼5 h after plating, when cells typically started to individually migrate. The cells of Dse-5MM-MO-injected CNC explants exhibited F-actin+ stress fibers throughout the cytoplasm, in addition to
